Communication devices such as terminals are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or mobile stations. Terminals are enabled to communicate wirelessly in a wireless or cellular communications network or a wireless communication system, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two terminals, between a terminal and a regular telephone and/or between a terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Examples of wireless communications networks are Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS) and Global System for Mobile communications (GSM).
Terminals may further be referred to as mobile telephones, cellular telephones, laptops, surf plates or tablets with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used to denote the transmission path from the base station to the mobile station. The expression Uplink (UL) is used to denote the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) LTE, base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks and related core network nodes, such as a Mobility Management Entity (MME) and a Serwing GateWay (SGW).
The MME is a control node and is responsible for idle mode UE tracking and paging procedure including retransmissions. The MME is involved in the bearer activation/deactivation process and is also responsible for choosing the SGW for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. The MME is responsible for authenticating the user.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
The introduction of new types of devices, such as devices that are used for Machine-Type-Communication (MTC), that interact with wireless communications networks put new requirements both on the devices, such as UEs, and the networks. Such new requirements may impose problems, such as shorter battery lifetime for the UEs, and from the network point of view one of the problems is to handle many devices sending small amounts of data.
For example, when a device, such as a UE, wants to send data, it needs to set up a connection towards the wireless communications network. This implies some mandatory steps, e.g. establishing a control connection to the MME through the eNodeB, establishing a secure radio connection on the air interface and configuring data bearers through which data may be sent. FIG. 1 shows a legacy normal service request establishment in LTE when data is to be received or transferred. As can be seen from FIG. 1 there is rather much signaling, i.e. actions 101-114, before the UE sends 115 the payload data to the eNodeB.
The signaling described above consumes much processing resources compared to the data volume being transferred for some devices, such as MTCs. This may then set a limit on how many devices that an eNodeB may handle, or how much other traffic the eNodeB may handle.
One prior art approach is to always have the devices in connected mode, that is e.g. have a control connection towards the MME, a secure radio connection and configured data bearers established all the time. This will however have impacts both on the performance of mobile devices, e.g. in terms of battery lifetime, and also on the performance of the network, since the connected mode consumes network resources. In fact, an eNodeB is normally designed to only handle a certain maximum number of users in connected mode. Since the actual number of devices in the area may be multiples higher than the designed maximum number of users in connected mode this will impose a large limitation.